1. Field of the Invention
The invention relates generally to dispensers and in particular to dispensers for semi-solid material in stick form which have a tubular barrel for housing the material and are provided with a drive mechanism for moving the material axially to and fro along the barrel for dispensing material at an open end of the barrel.
2. Description of the Prior Art
In a known dispenser of this type the drive mechanism comprises an actuator adapted to be rotated by hand, and an elevator which is driven axially of the barrel to move material therealong. The actuator comprises a knurled drive wheel held captive for rotation by an inwardly directed radial flange at one end of the barrel, and a threaded spindle extending axially inside the barrel. The elevator comprises a unitary moulding screwed onto the spindle such that rotation of the drive wheel causes the elevator to move axially along the barrel.
Dispensers of this type are particularly suited for dispensing deodorant and other semi-solid materials in stick form. The stick is formed in situ from a liquid, usually (but not necessarily) molten, which is introduced into the barrel and allowed to solidify. The stick must be sufficiently well attached to the elevator for the elevator to be able to push the stick along the barrel for use and to withdraw it $ub$equently against the frictional resistance presented by the interior of the barrel. A known method of manufacture is to assemble the dispenser by inserting the elevator into the barrel through the dispensing end thereof and to introduce the actuator through the opposite end of the barrel so that the elevator is engaged on the spindle and the drive wheel is located by the radial flange. The barrel is then top-filled with hot liquid through the dispensing end thereof. However, the assembly of the elevator with the actuator is a slow and expensive part of the process, and a stick filled in this way tends to shrink on cooling, with the result that its free surface adopts a concave profile. This is undesirable for aesthetic and practical reasons. It is thus desirable to fill the barrel when inverted, through the end in which the actuator is located when assembled. Bottom-fill of the dispenser through the central orifice provided in the elevator when the actuator is disassembled therefrom cannot be undertaken with the conventional design of dispenser, since this orifice is of insufficient dimension to allow uninterrupted flow of the product, which may be a suspension with a high solids content and liable to set on any obstruction which is presented.
One solution to this problem which has been adopted in the prior art is to omit the inwardly directed radial flange which holds the actuator captive, and to replace it with a suitable formation over which the drive wheel of the actuator is clipped and which thereafter holds the actuator captive for rotation. In this case the elevator and actuator can be preassembled together and clipped on to the barrel after filling when the product is still in a liquid phase. This of course is not possible when an inwardly directed radial flange is provided, since the elevator must then be inserted into the barrel through the dispensing end of the barrel.
In the absence of the radial flange the barrel presents a full diameter filling aperture, so that from the point of view of both filling speed and assembly, a modification of this kind has proved satisfactory for dispensers of essentially circular cross-section. However, the current move is strongly towards non-circular e.g. oval barrels, and for these dispensers the modification is not appropriate, requiring as it does a barrel cross-section which is circular to enable the drive wheel to rotate on it.